Motor compressor cooling in refrigerating apparatus



Oct. 30, 1956 MOODY 2,768,511

MOTOR COMPRESSOR COOLING IN REFRIGERATING APPARATUS Filed March 21, 1955IN V EN TOR.

ARTHUR M G. MOODY VMu/A" 41%.

A TTORNE YS United States Patent MOTOR COMPRESSQR COOLING INREFRIGERA'IING APPARATUS Arthur M. G. Moody, La Crosse, Wis., assignorto The Trane Company, La Crosse, Wis, a corporation of WisconsinApplication March 21, 1955, Serial No. 495L487 4 Claims. (Cl. 62117.8)

This invention relates to refrigerating apparatus of the type includinga motor-compressor assembly, and particularly to apparatus in which themotor and com pressor are housed in a sealed unit.

It is an object of this invention to provide means for cooling the motorusing the refrigerant of the apparatus as a heat exchange medium.

It is another object of the invention to provide fans on the motor shaftfor causing a circulation of refrigerant gas in a closed circuit overthe heat producing elements of the motor to cool said elements, thenthrough a heat exchanger to remove heat from the refrigerant gas.

It is another object of the invention to provide passageways in themotor casing to conduct refrigerant gas in two streams to the ends ofthe motor to flow first over the bearings and with each stream thenseparating into two streams one of which flows over the stator windingand the other of which flows through the gap and outwardly throughpassageways in the stator.

Other objects and advantages of the invention will appear as thespecification proceeds to describe the invention with reference to theaccompanying drawin in which Figure 1 is a partly diagrammatic view ofthe refrigoration apparatus of my invention.

Figure 2 is a cross-sectional view of the motor-compressor assemblytaken on an axial plane.

Referring now to Figure 1, an electric motor has at one end a firstcompressor stage 12 and at the other end a second compressor stage 14. Across-over pipe 16 conducts gas from the discharge of the first stage 12to the inlet of the second stage 14. The gas discharged from the secondstage 14 flows through a pipe 18 to a condenser Ztl. The condenser 20may be of the shelland-tube type in which cooling Water flows throughthe tubing 22 and the refrigerant is in the shell outside the tubes.Refrigerant liquid condensed in condenser 24? flows by gravity throughpipe 23 to a float chamber 24. Float 26 in float chamber 24- opens andcloses to control the flow of refrigerant liquid to an evaporator 28which is also of'the shell-and-tube type in which the secondaryrefrigerant liquid such as water or brine flows through the tubing 3%and the refrigerant is in the shell outside the tubing 30. The secondaryrefrigerant liquid circulates between the evaporator 23 and the coolingload served by the refrigeration apparatus to transfer heat from theload to the evaporator 28. In removing heat from the secondaryrefrigerant, the refrigerant in the evaporator 23 boils forming gaswhich passes through the liquid eliminator 32 and thence into thesuction pipe 34 to the inlet of the first stage compressor 12.

The motor 1% has a fluid tight casing 35 secured in fluid tightrelationship to compressor housings 12 and 14. A motor frame 38 issupported in said fluid tight casing 35 by a pair of rings 40 and 41which divide the annular space between motor frame 38 and said fluidtight easing into a central chamber 42 and end chambers croo r 44 and46. Motor frame 38 has bearings 48 and 50 which rotatably support ashaft 36. Shaft 36 extends at one end into compressor housing 12 and hasimpeller 52 secured thereto. The other end of shaft 36 extends intohousing 14 and has impeller 54 secured thereto. The ends of the shaft 30fit closely in the back plates 13 and 35 of the respective compressorhousings 12 and 14 to substantially prevent any flow of gas between thecasing 35 and the compressor housings 12 and 14. A stator 56 is securedto the motor frame 38. Stator 56 has the usual windings 58. A pluralityof radial passageways 60 extend through the stator 56. A rotor 62 ismounted on shaft 36 to rotate therewith. Rotor 62 rotates within stator56 and has an outside diameter slightly less than the inside diameter ofthe stator 56 to provide a gap between the rotor 62 and stator 56. Fans64 and 66 are mounted on shaft 36 to rotate therewith. Shrouds 6S and 79direct the gas into the fans 64 and 66. A duct 72 has a heat exchanger74 mounted therein. Duct '72 is connected to receive gas from centralchamber 42. A housing 76 surrounds duct 72 and provides passageways 78and with duct 72 for the gas leaving the heat exchanger 7 5 to flow tothe end chambers 44 and respectively. Heat exchanger 74 has tubes 82 forconducting fluid from a supply header 34 to a discharge header 36.Supply header is connected by pipe 83; to condenser to receive liquidrefrigerant from condenser Zil. A valve is interposed in pipe 5?; tocontrol the flow of liquid therethrough. if desired valve 9?! may be ofthe thermostatic type in which a temperature sensing bulb is mounted inthe gas stream leaving the discharge header 86. Discharge header isconnected by pipe 92 to the condenser 2d. The liquid rcfrigerant flowingupwardly in tubes 32 receive heat from the gas flowing over the outsidesurface of the tubes and is evaporated. The evaporated refrigerant gasflows to the condenser 2i") through pipe 92. The refrigerant in the pipe88, the tubes 82, and the pipe 92 flows by gravity, because the liquidin pipe 88 is more dense than the gas in pipe 92 and tubes 82.

The refrigerant gas flowing over the outside of tubes 82 of the heatexchanger 74 is cooled and flows through passageways 78 and 30 to endchambers 44 and 46 respectively. From end chambers 44 and 46 the gasflows over the bearings 4-8 and 5t removing heat therefrom. The gas thenflows through the fans 64 and 66. The gas leaving each fan divides intotwo streams. One stream flows over the windings 58 to remove heattherefrom and it then flows into the central chamber 42. The otherstream flows into the gap between the stator and rotor 62 and thenceoutwardly through passageways 6% into the central chamber 42. In passingthrough the gap and the passageways 60 the gas removes heat from boththe rotor and the stator. The gas collected in central chamber 42 flowsagain through the heat exchanger 74 which removes heat from the gasprior to its recirculation through the motor.

It is thus seen that the heat is effectively transferred from the areasin the motor at which it is generated to the refrigeration system servedby the compressor.

While the apparatus disclosed and described herein constitutes apreferred form of the invention, yet it will be understood that theapparatus is capable of alteration without departing from the scope orspirit of the invention, and that all modifications that fall within thescope of the appended claims are intended to be included herein.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. In refrigerating apparatus, the combination of an evaporator forvaporizing refrigerant, a condenser for liquefying refrigerant, acompressor for circulating refrigerant through said evaporator and saidcondenser, a motor for driving said compressor, a fluid tight casingenclosing said motor and compressor, a shaft and rotor assemblyrotatably mounted in said motor, a heat exchanger in said fluid tightcasing, a fan secured to said shaft and rotor assembly for circulatingrefrigerant gas from said motor through said heat exchanger and back tosaid motor, said heat exchanger having fluid passageways, a firstconduit between said condenser and said fluid passageways for conductingliquid refrigerant from said condenser to said fluid passageways and asecond conduit between said fluid passageways and said condenser forconducting refrigerant gas from said fluid passageways to saidcondenser.

2. In refrigerating apparatus, the combination of an evaporator forvaporizing refrigerant, a condenser for liquefying refrigerant, acentrifugal compressor for circulating refrigerant through saidevaporator and said condenser, a casing in fluid tight connection withsaid centrifugal compressor, a motor frame in said casing and spacedwith respect to said casing, partitions between said motor frame andsaid casing dividing the space therebetween into a central chamber andtwo end chambers, a stator secured to said frame and having radialpassageways therein communicating with said central chamber, bearingssecured to each end of the frame, a shaft and rotor assembly rotatablymounted in said bearings, said shaft and rotor assembly extending intosaid compressor, an impeller in said centrifugal compressor, saidimpeller being secured to said shaft and rotor assembly, fan meanssecured to said shaft and rotor assembly for moving gas from said endchambers into said radial passageways and thence into said centralchamber, a duct extending from said central chamber to said end chambersfor conducting gas from said central chamber to said end chambers, aheat exchanger in said duct, fluid passageways in said heat exchanger, afirst conduit between said condenser and said fluid passageways forconducting liquid refrigerant from said condenser to said fluidpassageways and a second conduit between said fluid passageways and saidcondenser for conducting refrigerant gas from said fluid passageways tosaid condenser.

3. In refrigerating apparatus, the combination of an evaporator forvaporizing refrigerant, a condenser for liquefying refrigerant, acentrifugal compressor having an inlet connected to receive refrigerantfrom said evaporator and a discharge chamber connected to transmitrefrigerant to said condenser, a substantially annular motor casingsecured in fluid tight engagement with said compressor, a motor frame insaid substantially annular motor casing, annular rings between saidmotor frame and said motor casing to support said motor frame in saidmotor casing, said annular rings being arranged to divide the annularspace between said motor frame and said motor easing into a centralchamber and two end chambers, a stator mounted in said motor frameopposite said central chamber, said stator having radial passagewayscommunicating with said central chamber bearings in each end of themotor frame, a shaft and rotor assembly rotatably mounted in saidbearings, said shaft and rotor assembly extending into said compressor,an impeller in said centrifugal compressor, said impeller being securedto said shaft and motor assembly, fans secured to said shaft and rotorassembly for moving the refrigerant gas from said end chambers throughthe gap between said stator and rotor and outwardly through the radialpassageways of said stator into the central chamber, a duct extendingfrom said central chamber to said end chambers for conducting gas fromsaid central chamber to said end chambers, a heat exchanger in saidduct, said heat exchanger having first fluid passageways through whichthe gas flows in moving from said central chamber to said end chambers,said heat exchanger having second fluid passageways, a first conduitbetween said condenser and said second fluid passageways for conductingrefrigerant liquid from said condenser to said second fluid passagewaysand a second conduit between said second fluid passageways and saidcondenser for conducting refrigerant gas from said fluid passageways tosaid condenser.

4. in refrigerating apparatus, the combination of an evaporator forvaporizing refrigerant, a condenser for liquefying refrigerant, acentrifugal compressor housing, a motor housing in fluid tightconnection with said centrifugal compressor housing, means forconducting refrigerant from said centrifugal compressor housing to saidcondenser, means for conducting refrigerant from said condenser to saidevaporator, means for conducting refrigerant from said evaporator tosaid compressor housing, a motor stator in said motor housing, a shaftand rotor assembly rotatably mounted in said motor stator and extendinginto said centrifugal compressor housing, a centrifugal impeller mountedin said centrifugal compressor housing and being nonrotatably secured tosaid shaft and rotor assembly for moving gas in a closed circuit fromsaid evaporator to said centrifugal compressor, thence to said condenserand thence to said evaporator, a heat exchanger in fluid communicationwith said motor housing, a fan secured to said shaft and rotor assemblyfor circulating gas over said motor stator, said shaft and rotorassembly, and said heat exchanger, said heat exchanger having fluidpassageways, a first conduit between said condenser and the fluidpassageways of said heat exchanger for conducting liquid refrigerantfrom said condenser to the fluid passageways of said heat exchanger anda second conduit between the fluid passageways of said heat exchangerand said condenser for conducting refrigerant gas from the fluidpassageways of said heat exchanger to said condenser.

References Cited in the file of this patent UNITED STATES PATENTS1,448,700 Seidner Mar. 13, 1923 1,451,577 Jantzen Apr. 10, 19231,652,134 Thompson Dec. 6, 1927 2,177,827 Hintze Oct. 31, 1939 2,249,882Buchanan July 22, 1941 2,306,632 McCormack Dec. 29, 1942

